Data has become a key asset in modern societies, economies, and governmental organizations. Big Data encompasses various kinds of complex and large scale information that are beyond the processing capabilities of conventional software and databases. Open Data on the other hand can make Big Data more useful and widely accessible. The combination of Open and Big data can benefit users, developers, companies and various kinds of organizations to carry out useful analysis of data pattern and trends, make intelligent decisions, and solve complex problems that can help societies and economies and speed up innovations. The aim of the Open and Big Data conference (OBD 2015) is to promote the state of the art in scientific and practical research of open and big data and to bring together researchers and practitioners from academia, industry, and public sector in an effort to present their research work and share research and development ideas.